You do know to use the VIVA method AFTER your icing has crusted, right?Heating buttercream is usually a 911 reserved for a product full of air bubbles. This is how I do it...1. bring the water in a bain marie to medium warm 2. place the bowl of BC over it and let it melt a bit, stiring gently with a silicone spatula, slowly and in the same direction . 3. place mixture in fridge and bring back to a firm state. 4. rebeat...making sure your beaters are completely covered by the mixture (ala sugarshack' technique.) Number 4 is key...or you end up with bubbles again.
What do you mean "crust up again after using the viva method"? 
Your icing should be allowed to crust BEFORE using the viva method. I'm a little confused on exactly how you're trying to smooth your icing.
I would not heat buttercream. After the shortening/butter is melted it changes and you're going to end up with a mess like luddroth said.
If you want "creamier" icing I suggest adding a little more milk or beating your shortening for about 15 minutes BEFORE adding any other ingredients when making your buttercream. I certainly wouldn't heat the bc. Humidity isn't a good combination with buttercream and heating it is going to give you problems in more way than one. Once shortening or butter has been melted it doesn't solidify back to the origional consistency. Have you ever had a stick of butter to melt (not just soft but melted) and put it back in the fridge to solidify? It sort of "seperates" if that makes sense.
Warming and rebeating can be done. Think about the technique to fix "broken" meringue buttercreams. Done all the time to save that product.
Warming and rebeating can be done. Think about the technique to fix "broken" meringue buttercreams. Done all the time to save that product.
I think it depends on which buttercream the OP is using. If you do a Meringue based BC I can see it working. Of course then you couldn't use Viva with that icing.
If you are doing the crisco/butter with powder sugar, the crisco butter will melt and the sugar will get hard and crunchy. Ask me how I know? 
I am sorry I should of clarified more.
My first attempt was to try the boiling icing because it looked so smooth and creamy, but my cooked egg/sugar mixture had lumps in it so I didn't continue.
So my next attempt will be to try the "Hi-Ratio Buttercream recipe".
In the past when I have tried buttercream, it wasn't as smooth tasting as I would of liked. "Maybe it's me i try to be a perfectionist." I have a cake to do on Saturday, so will be trying this out.
So I was maybe looking for some pointers to help make it even smoother.Thanks for all your help/insight/advice ladies. I knew I could depend on you all for the "real deal" on baking.
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